Effect of fluorine on dielectric properties of SiOF films

Abstract

The effect of fluorine addition on silicon oxide film properties as a function of SiF4/O2 gas flow ratio was investigated. The films were deposited by using electron cyclotron resonance plasma chemical vapor deposition with SiF4 and O2 as source gases diluted in Ar. Characterization of films was carried out in terms of various gas flow ratios (SiF4/O2=0.2–1.0). The microwave power and substrate temperature during deposition were fixed at 700 W and 300 °C, respectively. The chemical bonding structure of the films was evaluated by Fourier transform infrared spectroscopy (FTIR), fluorine concentration by x-ray photoelectron spectroscopy, and refractive index by ellipsometry. The dielectric constant was determined from C–V measurements at 1 MHz. FTIR spectra show that as the fluorine concentration increased, the intensities of the Si–F bonding peak and the shoulder peak (at around 1160 cm−1) of the Si–O stretching mode both increased. Refractive index and deposited film density decreased with increasing SiF4/O2 gas flow ratio. The SiOF film deposited at a SiF4/O2 gas flow ratio of 1.0 exhibited a fluorine content of 11.8 at. % and a dielectric constant of 3.14.